15 degree caudal angulationI've just read in Merrill's (11th ed., volume 1, page 486) that a 10-15 degree caudal angulation projects the diaphragm below the 7th, 8th, and 9th ribs when doing PA anterior rib radiography. This angulation seems like it would project the diaphragm higher onto the ribs, what with the posterior sloping of the diaphragm. Could anyone explain how this angulation aids in demonstrating the lower anterior ribs?